1. Field of the Invention
The present invention is generally directed to a device for driving a blood pump, which is used for blood circulation in a living body or for assisting blood circulation in a living body, such as an artificial heart pump or an in-aortic balloon pump. More particularly, the present invention is directed to a device which detects a volume of blood pumped from a blood pump, the device including an oil reservoir in which are provided a gas chamber, a liquid chamber, and a movable member separating the two chambers, pump means for pumping out an amount of blood stored in the liquid chamber of the oil reservoir to the blood pump, and a pressure accumulating chamber storing therein a gas pressure of the gas chamber of the oil reservoir by being brought into fluid communication with the gas chamber of the oil reservoir.
2. Background Art
In a blood pump which is in association with a living body, the pumping capacity is necessary for confirming whether or not the blood pump is properly operating and for detecting a current state of the living body.
In addition, in order to obtain the maximum volume of blood pumped from the blood pump, it is desired to fully utilize the pump by monitoring its stroke. That is to say, the desired control of the pump is to pump blood out when the blood pump is filled with blood, and immediately thereafter to pump blood into the blood pump.
Conventionally, a device has been provided which operates based on a blood flow amount measured by a flow instrument placed in a conduit between the blood pump and the living body. In addition, a method has been provided which measures a displacement of a piston of a blood pump by providing a position detection sensor, as U.S. Pat. No. 4,648,384. Moreover, in the publication entitled xe2x80x9cDiagnosis of Mechanical Failures of Total Artificial Heartsxe2x80x9d (Vol. XXXI, Trans. Am. Soc. Artif. Intern. Organs 1985, pp.79-81), an integrated value of an air flow amount is calculated when released to atmospheric pressure, in order to determine an air amount which is used to drive a blood pump.
However, in the first and second-mentioned methods, a precise measuring instrument has to be placed close to the patient, which requires long wiring between the instrument and a monitor which is spaced from the patient, resulting in a problem that the patient is limited in his/her actions or behavior in view of patient safety.
As for the third-mentioned method, the requirement of integrating the airflow amount causes problems such as measuring precision and measuring device equipment complexity.
Moreover, due to the fact that the blood load becomes larger when blood is pumped-out, if the blood pump is designed to be driven by a single bi-directional motor, its control becomes complex, which consumes much electric power, with the result that making a device for controlling such a motor smaller is difficult.
Due to the fact that the blood load becomes larger when blood is pumped-out, the rotation speed of the motor becomes much larger when blood is pumped-out than when blood is pumped-in, which causes the rotation speed of the motor to peak when blood is pumped-out, resulting in a problem that the pumped-out amount of blood fails to increase.
Thus, a need exists to provide a device for driving a blood pump which overcomes the aforementioned problems.
The present invention has been developed to satisfy the need noted above. A first aspect of the present invention provides a device for driving a blood pump which comprises an oil reservoir including therein a gas chamber and a liquid chamber which are separated by a movable member; pump means for pumping out a liquid stored in the liquid chamber of the oil reservoir to the blood pump; and a pressure accumulating chamber storing therein a gas pressure of the gas chamber of the oil reservoir by being brought into fluid communication with the gas chamber of the oil reservoir.
A second aspect of the present invention is to provide a device which further comprises pressure measuring means for determining the gas pressure in the gas chamber of the oil reservoir.
A third aspect of the present invention is to provide a device, wherein the pressure measuring means is provided in the pressure accumulating chamber in order to determine the gas pressure in the gas chamber of the oil reservoir.
A fourth aspect of the present invention is to provide a device for driving a blood pump which comprises a first port connected to the blood pump; a second port connected to a liquid chamber of an oil reservoir which is separated therein from a gas chamber by a movable member; pump means for establishing positive and negative pumping actions in alternate fashion, the positive pumping action and the negative pumping action sucking and discharging a liquid from the second port and the first port to discharge the liquid to the first port and the second poll, respectively; pressure measuring means for determining a pressure in the gas chamber of the oil reservoir; and a control device controlling the positive and negative pumping actions of the pump means on the basis of a signal issued from the pressure measuring means.
A fifth aspect of the present invention is to provide a device, wherein the control device calculates an amount of the liquid to be sucked from and discharged to the blood pump on the basis of a changed amount in the signal from the pressure measuring means.
A sixth aspect of the present invention is to provide a device, wherein the control device switches, on the basis of the signal from the pressure measuring means, the pumping means from a positive pumping action to a negative pumping action and vice versa.
A seventh aspect of the present invention is to provide a device, wherein the gas chamber is in association with the atmosphere by way of valve means so as to be brought into atmospheric pressure level when the pressure in the gas chamber becomes a negative pressure.
An eighth aspect of the present invention is to provide a device, wherein one of a capacity of the gas chamber and the pressure in the gas chamber is set in order that loads of the pumping means when doing the respective positive and negative pumping actions are made as equal as possible.
A ninth aspect of the present invention is to provide a separation chamber including a second liquid chamber and a second gas chamber which is separated by a second movable member, the second liquid chamber being connected to the first port, the second chamber being connected to the blood pump.
A tenth aspect of the present invention is to provide a device, wherein the control device sets an amount of air in the second gas chamber on the basis of the signal from the pressure measuring means.
In accordance with the first aspect of the present invention, the blood pump driving device is provided with a pressure accumulating chamber storing therein a gas pressure of the gas chamber of the oil reservoir by being brought into fluid communication with the gas chamber of the oil reservoir. This pressure accumulating chamber acts as a load of the pump means during its pump-in process wherein the liquid filled in the liquid chamber of the oil reservoir is discharged to the blood pump, while the resulting pressure or stored pressure in the pressure accumulating chamber assists the pump means during its pump-out process. This eliminates load unbalance in the pump means.
In accordance with the second aspect of the present invention, in addition to the structure of the first aspect, the blood pump driving device further includes the pressure measuring means for determining the gas pressure in the gas chamber of the oil reservoir, which makes it possible to establish a control based on the gas pressure in the gas chamber and to eliminate a sensor to be placed close to the patient.
In accordance with the third aspect of the present invention, in the blood pump driving device which is a modified structure of the second aspect, the pressure measuring means is provided in the pressure accumulating chamber in order to determine the gas pressure in the gas chamber of the oil reservoir. This makes it possible to establish a control based on the determined gas pressure in the gas chamber of the oil reservoir.
In accordance with the fourth aspect of the present invention, in the blood pump driving device, the control device controls the positive and negative pumping actions of the pump means on the basis of the signal issued from the pressure measuring means, the positive pumping action being made to discharge the liquid to the first port which is sucked from the second port, the negative pumping action being made to discharge the liquid to the second port which is sucked from the first port. This equalizes the loads of the pump means during its respective opposite direction rotations and makes it unnecessary to place a sensor near the patient.
In accordance with the fifth aspect of the present invention, in the blood pump driving control device which is of a modified structure of the fourth aspect, the control device calculates the amount of the liquid to be sucked from and discharged to the blood pump on the basis of the changed amount in the signal from the pressure measuring means. This makes it possible to establish a control based on the determined amount of liquid discharged to or sucked from the blood pump, thereby making a control of the amount of blood which is discharged to or sucked from the living body more precise.
In accordance with the sixth aspect of the present invention, in the blood pump driving device which is of a modified the structure of the fourth aspect, the control device switches, on the basis of the signal from the pressure measuring means, the pumping means from the positive pumping action to the negative pumping action and vice versa. This equalizes the loads of the pump means during its respective normal and reverse rotations.
In accordance with the seventh aspect of the present invention, in the blood pump driving device which is of a modified structure of the fourth aspect, the gas chamber is in association with the atmosphere by way of valve means so as to be brought to atmospheric pressure when the pressure in the gas chamber becomes negative pressure. This causes the pressure in the gas chamber not to be always negative, thereby properly maintaining the amount of gas in the gas chamber.
In accordance with the eighth aspect of the present invention, in the blood pump driving device which is of a modified structure of the fourth aspect, one of a capacity of the gas chamber and the pressure in the gas chamber is set in order that loads of the pumping means when doing the respective positive and negative pumping actions are made as equal as possible. This equalizes the loads of the pump means during its respective normal and reverse rotations.
In accordance with the ninth aspect of the present invention, in the blood pump driving device which is structured to add the separation chamber to the fourth aspect such that the separation chamber includes the second liquid chamber and the second gas chamber which is separated by a second movable member, the second liquid chamber being connected to the first port, the second chamber being connected to the blood pump. This makes it possible for the blood pump to be air-pressure operated.
In accordance with the tenth aspect of the present invention, in the blood pump driving device which is of a modified structure of the ninth aspect, the control device sets the amount of air in the second gas chamber on the basis of the signal from the pressure measuring means. This makes it possible to establish a control based on the set amount of air in the second gas chamber.